1. Field
Example embodiments relate to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a photomask for forming a semiconductor pattern.
2. Description of the Related Art
As the minimum dimension of a semiconductor pattern decreases according to the design rule of micromachining, the uniformity of a critical dimension (CD) of a photomask becomes more and more important. Non-uniformity of the CD results from accuracy limits of photomask manufacturing equipments and variation of the density distribution in the semiconductor pattern. The non-uniformity of the CD resulting from the density distribution in the semiconductor pattern may be controlled by an electron beam through a fogging effect correction and proximity effect correction of an electron beam.
FIG. 1 is a plan view illustrating a portion of a conventional photomask.
Referring to FIG. 1, a plurality of dies is formed on a photomask 1. Each of the plurality of dies includes a main pattern. Meanwhile, an area without a pattern is between the plurality of dies, and, hereinafter, is referred to as a dividing area for convenience. For example, a dividing area 12 without a pattern is between a first die 11a and a second die 11b, and each of the first and second dies 11a, 11b on the photomask includes a main pattern.
FIG. 2 is a graph showing variations of width of CD in forming a main pattern of two dies adjacent to a dividing area.
In FIG. 2, the horizontal axis denotes a direction along a row of dies in a photomask, and the vertical axis denotes the width of a CD value of a main pattern formed on a die. “A” represents an area of the main pattern formed in the first die 11a adjacent to the dividing area 12, “B” represents the area of dividing area 12, and “C” represents an area of the main pattern formed in the second die 11b adjacent to the dividing area 12. The selected patterns of the two dies are within 1000 μm from the dividing area 12. Referring to FIG. 2, as the main pattern is close to the dividing area 12, variation of the width of the CD of the main pattern formed in dies, in a same batch of photomask developing, is relatively large.
FIG. 3 is a view showing a develop loading error of two adjacent dies on a conventional photamask
FIG. 3 illustrates a CD of a main pattern, for example, a space pattern formed in the first die 11a and the second die 11b adjacent to the dividing area 12 after a development. The horizontal axis denotes a direction along a row of dies in a photomask, and the vertical axis denotes the width of the CD values of a main pattern formed on a die. As a distance from the dividing area 12 decreases, the CD of the space pattern formed in the first die 11a and the second die 11b increases. This is because the dividing area 12 does not have a space pattern, the equivalent average density of the space pattern in an area close to the dividing area 12 is lower than that of an area near the center of a die. Accordingly, a supplied developer may be consumed locally in a different rate near the dividing area 12 from that near the center of the die. The space pattern may be enlarged quicker near the dividing area 12 than the center of the die during a photomask development, resulting in a develop loading error of the space pattern. Such develop loading error increases sharply when the space pattern is within a first characteristic width W1 from the interface between the dividing area 12 and the die. Conventionally, W1 may be several hundreds of μm, and a develop loading error that increases at several hundreds μm away from the dividing area is referred to as a mid-local develop loading error.